HistologyReview – Dentalelle Tutoring

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Basics

The dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. It lies below a cellular aggregation known as the enamel organ. The dental papilla appears after 8-10 weeks intra uteral life.

The dental papilla gives rise to the dentin and pulp of a tooth.

The enamel organ, dental papilla, and dental follicle together forms one unit, called the tooth germ. This is of importance because all the tissues of a tooth and its supporting structures form from these distinct cellular aggregations.

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Teeth

Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth.

For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate stages of fetal development. Primary (baby) teeth start to form between the sixth and eighth week of prenatal development, and permanent teeth begin to form in the twentieth week.

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4 Stages

What characterizes the 4 stages of tooth development

1) Ball of cells: bud stage (initiation)2) Cap: the first time you can identify the three parts (DO, DP, DS)3) Early Bell: IEE makes the shape of the future crown.4) Late Bell: calcified tissue (young enamel, not fully mineralized)

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Bud Stage

http://www.fidanoski.ca/dentalhygiene/oralhistology/19-bell-stage.jpg

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Cap

http://www.fidanoski.ca/dentalhygiene/oralhistology/19-bell-stage.jpg

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Bell

http://www.fidanoski.ca/dentalhygiene/oralhistology/19-bell-stage.jpg

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Another form

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OEE AND IEE

Outer enamel Epithelium (OEE)

Simple cuboidal cells

Inner enamel epithelium (IEE)

Cuboidal ---> columnar (more active)Form the enamel of the tooth

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Photo

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More

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Columnar

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Stelate reticulum

Stelate reticulum

Star-shaped cells.

Attenuated by desmosomes (loosely connected)Functions to cushion the developing crown

The OEE and Stelate Reticulum in late crown development break up and there will be a remnants of both.

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Dental Laminas

1) dental lamina2) successional lamina3) Vestibular lamina4) Extension of the dental lamina

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Terms to remember

Dentinogenesis: The process of dentin formation.

Odontoblasts: Form dentin.

Odontogenesis: Formation of the entire tooth

Odontoblast: Cells that form dentin

Amelogenesis: Ameloblasts form enamel

Epithelial rests: remains of a structure.May be remains of dental lamina

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Dental Papilla

Becomes visible at the cap stage.

Name reserved for the area inside the IEE that eventually becomes the dental pulp

When enamel formation is complete this space is no longer referred to as dental papilla, and is called dental pulp

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Stages of Ameloblasts

1) Morphogenic stage2) Organizing stage3) Formative (secretory) stage (Tomes' processes appear)4) Maturative stage5) Protective stage6) Desmolytic stage

Where does the enamel start forming? It starts at the cusp tips/incisal edges

The ameloblasts and odontoblasts moving away from the DEJ in late crown development

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Stratum Intermedium

Cuboidal cells found in late bell stage between columnar ameloblasts (IEE) and stelate reticulum.

The stratum intermedium appears as a layer in the late cap/ early bell stage.

Seems to aid in enamel production

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Basement Membrane

As the enamel and dentin are laid down, the basement membrane is caught in between the two layers and breaks up

Basement membrane breaks down and is the future location of the DEJ

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Crown Formation

1) ectomesenchymal stem cells of Dental Papilla differentiate into odontoblasts2) predentin forms3) calcification of predentin yields dentin4) pre-ameloblasts stop mitosis ---> secretory ameloblasts ---> form "young enamel"

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References

http://anatomyandphysiologyi.com/wp-content/uploads/2013/06/simple-cuboidal-epithelium.jpg

http://www.fourthmolar.com/m/photos/view/bud-cap-and-bell-stage

http://en.wikipedia.org/wiki/Human_tooth_development#Cap_stage

Mosbys Textbook

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